The present invention relates to the art of package making with form, fill and seal machines of the type wherein a continuous sheet of package making film is shaped by a forming shoulder tubularly about a forming and filling tube, and is more particularly concerned with avoiding lateral displacement or drifting of the film sheet relative to the forming and filling tube during the shaping process.
A problem has existed heretofore due to tendency of package making sheet material of the type having a zipper area extending longitudinally therealong intermediate side edges, tending to drift or shift laterally while being shaped tubularly about the forming and filling tube or nozzle of a form, fill and seal machine. In the course of shaping of the sheet material, the longitudinal side edges of the material, which lack any means for guiding the sheet, are brought into seaming relation. The zipper is intended for reclosable fastening of the mouth ends of packages ultimately formed from the material, while the seamed side edges of the material will form closed ends of the packages. Sides of the packages are sealed closed by the customary sealing bar and pull down mechanism of the machine. By way of information, and not limitation, a disclosure of the general type of form, fill and seal package making machine with which the present invention may be useful is disclosed in U.S. Pat. No. 4,829,745, which to any extent necessary for thorough understanding of the present disclosure is incorporated herein by reference. Therefore, the present disclosure may be directed more simply to the present invention.